5.2 Translation between Work and Heat 5.2.1 The First Law of thermodynamics Conservation and transformation of energy Do the process according with the First Law can occur spontaneously spontaneous process: A process which can occur automatically without any outside effect In nature,the spontaneous processes exist direction
5.2.1 The First Law of thermodynamics Conservation and transformation of energy Do the process according with the First Law can occur spontaneously ? 5.2 Translation between Work and Heat spontaneous process: A process which can occur automatically without any outside effect In nature, the spontaneous processes exist direction
Produce heat by friction Power plant Work Heat Work Heat 100% 40% Spontaneous process exists direction, condition and bounds. How do we describe the dir ertion,conditions and bounds of Spontaneous prccess The Second Law of Thermodynamics
Spontaneous process exists direction, condition and bounds. Heat Power plant Work 40% Produce heat by friction Heat 100% Work How do we describe the direction, conditions and bounds of Spontaneous process The Second Law of Thermodynamics
5.2.2 The Second Law of thermodynamics Statements of the Second Law There are 60-70 statements of the Second Law in 1851 Kelvin-Planck Statement according to transformation of work and heat No apparatus can operate in such a way that its only effect is to convert heat absorbed by a system completely into work done by the system. im1850 Clausius statement according to heat transfer No process is possible which consists solely in the transfer of heat from one temperature level to a higher one
Statements of the Second Law There are 60-70 statements of the Second Law in 1850 Clausius statement according to heat transfer No process is possible which consists solely in the transfer of heat from one temperature level to a higher one 5.2.2 The Second Law of thermodynamics in 1851 Kelvin －Planck Statement according to transformation of work and heat No apparatus can operate in such a way that its only effect is to convert heat absorbed by a system completely into work done by the system
热力学第二定律 开尔文说法：不可能从单一热源吸热使之完全变为 有用的功而不引起其他变化。 ·克劳修斯说法：热不可能自动从低温物体传给高温 物体
热力学第二定律 • 开尔文说法：不可能从单一热源吸热使之完全变为 有用的功而不引起其他变化。 • 克劳修斯说法：热不可能自动从低温物体传给高温 物体
第二类永动机？？？ 如果三峡水电站用降温法发电，使水 温降低5C,发电能力可提高11.7倍。 设mkg水的位差为180米 重力势能转化为电能： 21000 E=mgh=1800m[J] 2=11.7 E 1800 mkg水降低5C放热： Q=cm△t=21000m[J]
第二类永动机??? 如果三峡水电站用降温法发电，使水 温降低 5 ° C，发电能力可提高11.7倍。 设m kg水的位差为180 米 重力势能转化为电能： E = = mgh m J 1800 [ ] mkg水降低 5 ° C放热： Q cm t m J = Δ= 21000 [ ] 21000 11.7 1800 Q m E m = =